Adjustable Primary Air Supply for Wood Burning Device

ABSTRACT

An improved adjustable primary air supply for wood burning device comprises a base plate having an opening from where primary air enters a firebox. A gate rotationally attached to the base plate by way of a mechanical fastener; a slider with guiding means sliding within an inclined slot; the slider comprised of a contact point which makes contact with the gate for adjustments. A first thermostatic bimetal blade reacting to heat by displacing the gate so that the gate closes the opening; and a means to move the slider and push the gate fully open. The improvement comprising a first stopper member located on the base plate adjacent the opening and adapted to stop the movement of the gate and thereby prevent the gate from completely covering the opening, and a second thermostatic bimetal blade attached to the gate and adapted to react to heat by displacing the gate from the base plate so that the gate can move over the first stopper member such that the gate can continue to cover the opening until the gate contacts the slider contact point.

FIELD OF THE INVENTION

The present invention relates generally to wood burning appliances butmore particularly to an adjustable control that provides variable airintake resulting in efficient and clean burning.

BACKGROUND OF THE INVENTION

This invention is an improvement over Applicant's own U.S. Pat. No.7,325,541, issued Feb. 5, 2008, by solving issues only partiallyresolved before by Applicant or by other prior art.

A problem would arise with the original invention. Even as the burn ratewas reduced, the thermostatic bimetal blade would continue closing thegate due to the ambient and surface temperature and would choke the fireand cause an unclean burn as a result.

SUMMARY OF THE INVENTION

In view of the foregoing disadvantages inherent in the known devices nowpresent in the prior art, the present invention, which will be describedsubsequently in greater detail, is to provide objects and advantageswhich are:

To provide for an improved mechanical system to adjust air entry forefficient and clean burning.

To provide for an improved safety mechanism has been implemented in thenew design of the PA control to prevent damage to the thermostaticbimetal blade.

To attain these ends, the present invention generally comprises a baseplate having an opening from where primary air enters a firebox. A gaterotationally attached to the base plate by way of a mechanical fastener;a slider with guiding means sliding within an inclined slot; the slidercomprised of a contact point which makes contact with the gate foradjustments. A first thermostatic bimetal blade reacting to heat bydisplacing the gate so that the gate closes the opening; and a means tomove the slider and push the gate fully open. The improvement comprisinga first stopper member located on the base plate adjacent the openingand adapted to stop the movement of the gate and thereby prevent thegate from completely covering the opening, and a second thermostaticbimetal blade attached to the gate and adapted to react to heat bydisplacing the gate from the base plate so that the gate can move overthe first stopper member such that the gate can continue to cover theopening until the gate contacts the slider contact point.

The adjustable primary air supply improvement further including a safetymechanism comprising a bracket member attached to the first bimetalblade. A pivot rod attached between the base plate and the bracketmember and adapted to allow the first bimetal blade to pivot therearound. A second stopper member adapted to stop the bimetal blade frompivoting past a predetermined point; and a spring member attached at oneend to the bracket member and at an opposite end to a point on the baseplate at a distance therefrom and is adapted to hold the bracket againstthe second stopper member and to prevent the bimetal blade fromdeforming.

The adjustable primary air supply for a wood burning device having thefollowing method of operation: When starting a fire, the gate is openedto bring in as much air as possible; the first bimetal blade bends asthe temperature rises; the first bimetal blade pushes the gate partiallyover the opening until it hits the first stopper member; the secondbimetal blade bends as the temperature continues to increase until thespace created between the blade and the base plate is great enough toallow the gate to overpass the first stopper member and continue tofurther cover the opening until the blade contacts the slider contactpoint and stops; and when the first and second bimetal blades getscolder, they retract to their original configurations but the gate staysat the same position.

The adjustable primary air supply for a wood burning device has themeans to move the slider and push the gate fully open include a key. Thekey being turned to rotate a cog wheel which engages into a track whichincludes a plurality of holes.

The amount of the primary air is varied by the position of the slider.

The method of operation further includes: at minimum burn rate, the gatebeing completely closed by the first thermostatic bimetal blade, but thegate being raised by the second thermostatic bimetal blade therebyallowing a small amount of primary air to still enter the firebox. Bythe end of the burning cycle, as the temperature drops, the secondthermostatic bimetal blade returns to a bent shape which allows the gateto close the opening completely.

The gate is adapted to be pushed by the key when the key is pushedinwardly.

The first stopper member is an angled tab formed and bent from thematerial of the base plate.

The second stopper member is generally shaped as a hook member formedintegrally with and bent perpendicular from the base plate.

The point on the base plate includes a base spring bracket adapted toconnect to the opposite end of the spring member.

There has thus been outlined, rather broadly, the more importantfeatures of the invention in order that the detailed description thereofthat follows may be better understood, and in order that the presentcontribution to the art may be better appreciated. There are additionalfeatures of the invention that will be described hereinafter and whichwill form the subject matter of the claims appended hereto.

In this respect, before explaining at least one embodiment of theinvention in detail, it is to be understood that the invention is notlimited in its application to the details of construction and to thearrangements of the components set forth in the following description orillustrated in the drawings. The invention is capable of otherembodiments and of being practiced and carried out in various ways.Also, it is to be understood that the phraseology and terminologyemployed herein are for the purpose of description and should not beregarded as limiting.

As such, those skilled in the art will appreciate that the conception,upon which this disclosure is based, may readily be utilized as a basisfor the designing of other structures, methods and systems for carryingout the several purposes of the present invention. It is important,therefore, that the claims be regarded as including such equivalentconstructions insofar as they do not depart from the spirit and scope ofthe present invention.

Further, the purpose of the foregoing abstract is to enable the U.S.Patent and Trademark Office and the public generally, and especially thescientists, engineers and practitioners in the art who are not familiarwith patent or legal terms or phraseology, to determine quickly from acursory inspection the nature and essence of the technical disclosure ofthe application. The abstract is neither intended to define theinvention of the application, which is measured by the claims, nor is itintended to be limiting as to the scope of the invention in any way.

These together with other objects of the invention, along with thevarious features of novelty which characterize the invention, arepointed out with particularity in the claims annexed to and forming apart of this disclosure. For a better understanding of the invention,its operating advantages and the specific objects attained by its uses,reference should be made to the accompanying drawings and descriptivematter which contains illustrated preferred embodiments of theinvention.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 Perspective view of the device.

FIGS. 2 a-c Top views of the device with the PA open, partially closed,and closed.

FIGS. 3 a-c Top view, side view, and cutaway.along line EE, gatepartially closed.

FIGS. 4 a-c Top view, side view, and cutaway.along line UU, gatepartially closed.

FIGS. 5 a-c Top view, side view, and side view detail “T” of the gatefully closed.

FIGS. 6 a-c Isometric view and details “H” and “J” of the gate fullyclosed.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

An adjustable primary air supply for wood burning device (10) has a baseplate (12) into which is an opening (14) from where PA enters a firebox(not shown). An “L” shaped gate (16) is rotationally attached to thebase plate (12) by way of a mechanical fastener (18) which holds thegate (16) somewhat loosely in order to allow for easy rotation but alsofor another reason which will be described later. A slider (20) slides,as guided within an angled slot (22) by guiding means (23) generally inthe form of shoulder screws, rivets or short pegs. The slider (20) iscomprised of a roller contact point (21) which makes contact with thegate (16) in order to limit displacement range of the gate (16) as maybe required. A first thermostatic bimetal blade (28) reacts to heat bybending in a plane parallel to the base (12). The first thermostaticbimetal blade (28) is rotationally attached to the base plate (12) byway of a pivot rod (11).

FIG. 2 a illustrates the configuration when starting a fire, at whichpoint the PA is open to bring in as much air as possible. In order tofully open the PA, the gate (16) is pushed by a means, in the form of akey (30) in this figure, being pushed inwardly in the direction of arrow(17). As the firebox gets warmer, The first thermostatic bimetal blade(28) begins to bend as per FIG. 2 b, this pushes the gate (16) whichcloses the opening (14), this will also push the key (30) outwardly. InFIG. 2 b, the gate (16) only partially blocks the opening (14) becausethe slider (20) is so positioned so as to block any further displacementof the gate (16). In FIG. 2 c we see that by moving the slider (20)along the inclined slot (22), the gate (16) is allowed to fully closethe opening (14) as long as there is enough heat to bend the firstthermostatic bimetal blade (28) to do so.

In order to vary the position of the slider (20), the key (30) is turnedto rotate a cog wheel (32) which engages into a track (34) composed of aplurality of slits (36). For design purposes, the handle part (38) ofthe key (30) can be made into a knob for easier handling by a user.

The amount of the PA varies depending on the position of the slider(20). It is possible for the user to establish the optimum position ofthe slider (20) depending on the heating requirements. When the firstbimetal blade (28) gets colder, it retracts to its originalconfiguration but the gate (16) stays at the same position. That way,the PA is reduced to the minimum amount required for minimum burn rate.

The main feature of the device (10) is that it can provide maximum airto start the fire and it can reduce the burn rate to the user settingautomatically. The device (10) also prevents the user to reduce the burnrate unless proper burning has been established. Only the action of thefirst thermostatic bimetal blade (28) can reduce the burn rate. When thedesired burn rate is established and set by the user, the device willregulate the burn rate automatically and consistently. The only actionrequired by the user is to activate the control by pushing the controlkey (30) inwards when starting the fire or when adding a new load ofwood.

A second thermostatic bimetal blade (40) extending from the gate (16),to which it is mechanically attached, raises the gate (16) slightly asper FIGS. 4 a-c. Since, as mentioned earlier, mechanical fastener (18)holds gate (16) somewhat loosely, downward pressure exerted by thesecond thermostatic bimetal blade (40) pushes the gate (16) upward sothat it can continue its course beyond a second stopper member (52)which normally stops the gate (16), as seen in FIG. 2 b, when it is notlifted by the second bimetal blade (40). By no longer being stopped bythe second stopper member (52), the gate (16) can move further over theopening (14) until stopped by the roller contact point (21) which is ata location adjusted by the key (30). But, in this configuration, whichoccurs at the minimum burn rate, the gate (16) is slightly raised by thesecond bimetal blade (40) allowing a small amount of PA to enter thefirebox, which is sufficient to maintain proper combustion. By the endof the burning cycle, as the temperature drops, the second bimetal blade(40) returns to a bent shape which allows the gate (16) to closecompletely.

As the temperature increases, the thermostatic bimetal blade (28) wouldcontinue to bend and press against the gate (16) even after it hadreached the preset setting. This constriction of movement of thethermostatic bimetal blade (28) after the gate had been closed to thepreset setting made the thermostatic bimetal blade (28) bend in theopposite direction and deform, preventing the thermostatic bimetal blade(28) to perform as it was intended to. In order to remedy that problem,a safety mechanism consists of a first stopper member (50), a bracketmember (54), a spring (56) and a pivot rod (11).

The first stopper member (50) is located on the base (12) at the foot ofthe bracket member (54) and determines the rest position of thethermostatic bimetal blade (28). The spring (56) is attached to thebracket member (54) at one of its end and runs over and across the base(12) to attach its opposite end to a spring bracket (60) which extendsperpendicularly from the base (12).

The spring (56) pulls the thermostatic bimetal blade (28) against thefirst stopper member (50) to its rest position. This allows for thethermostatic bimetal blade (28) to pivot around the pivot rod (58) whenit gets overheated and prevents it from deforming.

While the fire burns reasonably hot and the gate (16) has been closed tothe preset setting, the burn rate can be altered by rotating the key(30). At this point, the thermostatic bimetal blade (28) pushes the gate(16) against the roller contact point (21) and the amount of combustionair is determined by the position of the slider (20). it must be notedthat this control prevents the user from reducing the burn rate andconsequently inducing unclean burning. Only when proper burning has beenestablished, the thermostatic bimetal blade (28) will bend and reducethe burn rate to the user's preset setting.

As to a further discussion of the manner of usage and operation of thepresent invention, the same should be apparent from the abovedescription. Accordingly, no further discussion relating to the mannerof usage and operation will be provided.

With respect to the above description then, it is to be realized thatthe optimum dimensional relationships for the parts of the invention, toinclude variations in size, materials, shape, form, function and mannerof operation, assembly and use, are deemed readily apparent and obviousto one skilled in the art, and all equivalent relationships to thoseillustrated in the drawings and described in the specification areintended to be encompassed by the present invention.

Therefore, the foregoing is considered as illustrative only of theprinciples of the invention. Further, since numerous modifications andchanges will readily occur to those skilled in the art, it is notdesired to limit the invention to the exact construction and operationshown and described, and accordingly, all suitable modifications andequivalents may be resorted to, falling within the scope of theinvention.

1. In an adjustable primary air supply for a wood burning devicecomprising a base plate having an opening from where primary air entersa firebox; a gate rotationally attached to said base plate by way of amechanical fastener; a slider with guiding means sliding within aninclined slot; said slider comprised of a contact point which makescontact with said gate for adjustments; a first thermostatic bimetalblade reacting to heat by displacing said gate so that said gate closessaid opening; and a means to move said slider and push said gate fullyopen; the improvement comprising a first stopper member located on saidbase plate adjacent said opening and adapted to stop the movement ofsaid gate and thereby prevent said gate from completely covering saidopening; and a second thermostatic bimetal blade attached to said gateand adapted to react to heat by displacing said gate from said baseplate so that said gate can move over said first stopper member suchthat said gate can continue to cover said opening until said gatecontacts said slider contact point.
 2. The adjustable primary air supplyimprovement of claim 1, further including a safety mechanism comprisinga bracket member attached to a said first bimetal blade; a pivot rodattached between said base plate and said bracket member and adapted toallow said first bimetal blade to pivot there around; a second stoppermember adapted to stop said bimetal blade from pivoting past apredetermined point; and a spring member attached at one end to saidbracket member and at an opposite end to a point on said base plate at adistance therefrom and is adapted to hold said bracket against saidsecond stopper member and to prevent said bimetal blade from deforming.3. An adjustable primary air supply for a wood burning device as inclaim 1, and having the following method of operation: when starting afire, said gate is opened to bring in as much air as possible; saidfirst bimetal blade bends as the temperature rises; said first bimetalblade pushes said gate partially over said opening until it hits saidfirst stopper member; said second bimetal blade bends as the temperaturecontinues to increase until the space created between said blade andsaid base plate is great enough to allow said gate to overpass saidfirst stopper member and continue to further cover said opening untilsaid blade contacts said slider contact point and stops; and when saidfirst and second bimetal blades gets colder, they retract to theiroriginal configurations but said gate stays at the same position.
 4. Theadjustable primary air supply for a wood burning device as in claim 1,wherein said means to move said slider and push said gate fully openincludes a key; said key being turned to rotate a cog wheel whichengages into a track which includes a plurality of holes.
 5. Theadjustable primary air supply for a wood burning device as in claim 1,wherein the amount of said primary air is varied by the position of saidslider.
 6. The adjustable primary air supply for a wood burning deviceas in claim 3, wherein the method of operation further includes: atminimum burn rate, said gate being completely closed by said firstthermostatic bimetal blade, but said gate being raised by said secondthermostatic bimetal blade thereby allowing a small amount of primaryair to still enter said firebox; by the end of the burning cycle, as thetemperature drops, said second thermostatic bimetal blade returns to abent shape which allows said gate to close said opening completely. 7.The adjustable primary air supply for a wood burning device as in claim4, wherein said gate is adapted to be pushed by said key when said keyis pushed inwardly.
 8. The adjustable primary air supply for a woodburning device as in claim 1, wherein said first stopper member is anangled tab formed and bent from the material of said base plate.
 9. Theadjustable primary air supply for a wood burning device as in claim 2,wherein said second stopper member is generally shaped as a hook memberformed integrally with and bent perpendicular from said base plate. 10.The adjustable primary air supply for a wood burning device as in claim2, wherein said point on said base plate includes a base spring bracketadapted to connect to said opposite end of said spring member.